Troubleshooting delamination problems

Delamination, sometimes referred to as lamination or layering, is a defect in which the surface of a molded part can be peeled off layer by layer.

Causes

• High shear stress.
• Incompatible materials blended together.
• Excessive use of mold release agent.
• Excessive material moisture. Excessive moisture heats up and forms steam, which results in delamination on the surface.
• Material degradation. This can be caused by excessive injection speed, residence time or melt temperature. Improper screw or runner system design may also lead to material degradation.

Remedies

Eliminate Degradation and Excessive Shear Stress

• Reduce shear stress.
• Remove excessive moisture. Material suppliers can provide optimum drying conditions for the specific materials.
• Reduce regrind material.
• Avoid excessive use of mold release agent. Repair the ejection system or other problems to eliminate the difficulty of de-molding instead of over-using the mold release agent.
• Avoid material contamination.

Solving one problem can often introduce other problems to the injection molding process. Each option hence requires consideration of all relevant aspects of the mold design specification.